The invention relates to sheet handling apparatus such as sheet acceptors, sorters, recirculators and the like. Such sheet handling apparatus is used in a variety of applications, particularly for handling documents of value such as banknotes, cheques, postal orders and the like.
Due to the varying condition of sheets, a common problem with sheet handling apparatus is the risk of sheets jamming. In some cases, the apparatus will normally shut down and the jammed sheet will need to be manually removed. This leads to significant downtime and often requires a specialist user to deal with the problem.
In more sophisticated systems, an auto purge process can be enabled. Thus, when a jam condition is sensed, the auto purge process will be run in an attempt to release the jam. If the system determines that the jam has been released, then the transaction will be continued but otherwise the transaction will be stopped. However, a problem has arisen with this approach in that the system for sensing the presence of a jam can occasionally suggest that the jam has been cleared when in fact it has not. This may be because a sensor is located at a position such that the auto purge process has moved a sheet just clear of the sensor but the cause of the jam has not been removed. As a result, the system can enter an endless loop which has to be manually detected and dealt with.
In accordance with the present invention, sheet handling apparatus including a transport system for transporting sheets; a sensing system for monitoring the passage of sheets; and a controller system for determining, during a transaction involving the transport of one or a sequence of sheets, the existence of a jam condition from the sensing system, and, if a jam condition exists,
a) operating the transport system to attempt to release the jammed sheet,
b) determining if a jam condition still exists, and
ci) if it does, stopping the transaction and,
cii) if it does not, attempting to continue the transaction
and wherein if the controller system determines that during a transaction a predetermined number of attempts to release the jammed sheet have been made, the controller system stops the transaction.
In order to avoid the endless loop problem mentioned above, in the present invention the controller system monitors the number of attempts made to release a jam and if a predetermined number is reached, it will stop the transaction. In this way, the system avoids entering an endless loop.
Typically, the predetermined number of attempts is three although two or more could also be chosen.
In order to attempt to recover from a jam condition the transport system is suitably controlled. For example, the transport system can be moved temporarily in reverse or slowly or rapidly to and from. Where the transport system includes one or more sheet stores and associated diverters, the control system may cause the or each diverter to move to and from, for example in a fluttering motion.
If the transport system includes one or more sheet stores in the form of roll storage modules (such as described in U.S. Pat. Nos. 4,669,393 and 4,871,125) then the control system may cause the or each roll storage module to operate in a direction opposite to its current operating direction.
The controller system may be implemented using a single controller such as a microprocessor but would typically be implemented in a distributed manner as described in more detail below.